diff --git a/src/panels/lovelace/entity-rows/hui-timer-entity-row.js b/src/panels/lovelace/entity-rows/hui-timer-entity-row.js
deleted file mode 100644
index fbcfd143d5..0000000000
--- a/src/panels/lovelace/entity-rows/hui-timer-entity-row.js
+++ /dev/null
@@ -1,98 +0,0 @@
-import { html } from "@polymer/polymer/lib/utils/html-tag";
-import { PolymerElement } from "@polymer/polymer/polymer-element";
-
-import "../components/hui-generic-entity-row";
-
-import timerTimeRemaining from "../../../common/entity/timer_time_remaining";
-import secondsToDuration from "../../../common/datetime/seconds_to_duration";
-
-class HuiTimerEntityRow extends PolymerElement {
-  static get template() {
-    return html`
-      <hui-generic-entity-row hass="[[hass]]" config="[[_config]]">
-        ${this.timerControlTemplate}
-      </hui-generic-entity-row>
-    `;
-  }
-
-  static get timerControlTemplate() {
-    return html`
-      <div>[[_computeDisplay(_stateObj, _timeRemaining)]]</div>
-    `;
-  }
-
-  static get properties() {
-    return {
-      hass: Object,
-      _config: Object,
-      _stateObj: {
-        type: Object,
-        computed: "_computeStateObj(hass.states, _config.entity)",
-        observer: "_stateObjChanged",
-      },
-      _timeRemaining: Number,
-    };
-  }
-
-  disconnectedCallback() {
-    super.disconnectedCallback();
-    this._clearInterval();
-  }
-
-  _stateObjChanged(stateObj) {
-    if (stateObj) {
-      this._startInterval(stateObj);
-    } else {
-      this._clearInterval();
-    }
-  }
-
-  _clearInterval() {
-    if (this._updateRemaining) {
-      clearInterval(this._updateRemaining);
-      this._updateRemaining = null;
-    }
-  }
-
-  _startInterval(stateObj) {
-    this._clearInterval();
-    this._calculateRemaining(stateObj);
-
-    if (stateObj.state === "active") {
-      this._updateRemaining = setInterval(
-        () => this._calculateRemaining(this._stateObj),
-        1000
-      );
-    }
-  }
-
-  _calculateRemaining(stateObj) {
-    this._timeRemaining = timerTimeRemaining(stateObj);
-  }
-
-  _computeDisplay(stateObj, time) {
-    if (!stateObj) return null;
-
-    if (stateObj.state === "idle" || time === 0) return stateObj.state;
-
-    let display = secondsToDuration(time);
-
-    if (stateObj.state === "paused") {
-      display += " (paused)";
-    }
-
-    return display;
-  }
-
-  _computeStateObj(states, entityId) {
-    return states && entityId in states ? states[entityId] : null;
-  }
-
-  setConfig(config) {
-    if (!config || !config.entity) {
-      throw new Error("Entity not configured.");
-    }
-    this._config = config;
-  }
-}
-customElements.define("hui-timer-entity-row", HuiTimerEntityRow);
diff --git a/src/panels/lovelace/entity-rows/hui-timer-entity-row.ts b/src/panels/lovelace/entity-rows/hui-timer-entity-row.ts
new file mode 100644
index 0000000000..7e7383961d
--- /dev/null
+++ b/src/panels/lovelace/entity-rows/hui-timer-entity-row.ts
@@ -0,0 +1,128 @@
+import {
+  html,
+  LitElement,
+  TemplateResult,
+  property,
+  PropertyValues,
+} from "lit-element";
+
+import "../components/hui-generic-entity-row";
+import "../components/hui-warning";
+
+import timerTimeRemaining from "../../../common/entity/timer_time_remaining";
+import secondsToDuration from "../../../common/datetime/seconds_to_duration";
+import { HomeAssistant } from "../../../types";
+import { EntityConfig } from "./types";
+import { HassEntity } from "home-assistant-js-websocket";
+
+class HuiTimerEntityRow extends LitElement {
+  @property() public hass?: HomeAssistant;
+  @property() private _config?: EntityConfig;
+  @property() private _timeRemaining?: number;
+  private _interval?: number;
+
+  public setConfig(config: EntityConfig): void {
+    if (!config) {
+      throw new Error("Configuration error");
+    }
+    this._config = config;
+  }
+
+  public disconnectedCallback(): void {
+    super.disconnectedCallback();
+    this._clearInterval();
+  }
+
+  protected render(): TemplateResult | void {
+    if (!this._config || !this.hass) {
+      return html``;
+    }
+
+    const stateObj = this.hass.states[this._config.entity];
+
+    if (!stateObj) {
+      return html`
+        <hui-warning
+          >${this.hass.localize(
+            "ui.panel.lovelace.warning.entity_not_found",
+            "entity",
+            this._config.entity
+          )}</hui-warning
+        >
+      `;
+    }
+
+    return html`
+      <hui-generic-entity-row .hass="${this.hass}" .config="${this._config}">
+        <div>${this._computeDisplay(stateObj)}</div>
+      </hui-generic-entity-row>
+    `;
+  }
+
+  protected updated(changedProps: PropertyValues) {
+    super.updated(changedProps);
+
+    if (changedProps.has("hass")) {
+      const stateObj = this.hass!.states[this._config!.entity];
+      const oldHass = changedProps.get("hass") as this["hass"];
+      const oldStateObj = oldHass
+        ? oldHass.states[this._config!.entity]
+        : undefined;
+
+      if (oldStateObj !== stateObj) {
+        this._startInterval(stateObj);
+      } else if (!stateObj) {
+        this._clearInterval();
+      }
+    }
+  }
+
+  private _clearInterval(): void {
+    if (this._interval) {
+      window.clearInterval(this._interval);
+      this._interval = undefined;
+    }
+  }
+
+  private _startInterval(stateObj: HassEntity): void {
+    this._clearInterval();
+    this._calculateRemaining(stateObj);
+
+    if (stateObj.state === "active") {
+      this._interval = window.setInterval(
+        () => this._calculateRemaining(stateObj),
+        1000
+      );
+    }
+  }
+
+  private _calculateRemaining(stateObj: HassEntity): void {
+    this._timeRemaining = timerTimeRemaining(stateObj);
+  }
+
+  private _computeDisplay(stateObj: HassEntity): string | null {
+    if (!stateObj) {
+      return null;
+    }
+
+    if (stateObj.state === "idle" || this._timeRemaining === 0) {
+      return this.hass!.localize("state.timer." + stateObj.state);
+    }
+
+    let display = secondsToDuration(this._timeRemaining || 0);
+
+    if (stateObj.state === "paused") {
+      display += ` (${this.hass!.localize("state.timer.paused")})`;
+    }
+
+    return display;
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "hui-timer-entity-row": HuiTimerEntityRow;
+  }
+}
+
+customElements.define("hui-timer-entity-row", HuiTimerEntityRow);
diff --git a/src/translations/en.json b/src/translations/en.json
index 35207ed514..9797982c17 100644
--- a/src/translations/en.json
+++ b/src/translations/en.json
@@ -271,6 +271,11 @@
       "off": "[%key:state::default::off%]",
       "on": "[%key:state::default::on%]"
     },
+    "timer": {
+      "active": "active",
+      "idle": "idle",
+      "paused": "paused"
+    },
     "vacuum": {
       "cleaning": "Cleaning",
       "docked": "Docked",